The investigators plan to study the variability of lung function parameters and bronchial inflammatory markers in 20 patients with bronchiolitis obliterans at the age of 6 to 25 years compared with an age- and sex-matched control group. The investigators will perform a pulmonary function test (body plethysmography with TLCO), and measure the fraction of exhaled nitric oxide (eNO). Further a blood sample is drawn to determine the systemic inflammation. Finally induced sputum is collected and a cell count is performed, and cells and supernatants are analyzed for inflammatory markers. This investigation will be repeated after 4-6 weeks. The aim of this study is to define baseline values and the variability of possible outcome parameters for future interventional studies.

The purpose of this study is to characterize the variability of lung function values and bronchial inflammation of 20 Patients with Bronchiolitis obliterans aged between 6 up to 25 years. The patients' data will be compared with the results of a reference group with similar age conditions to determine possible outcome-parameters for following interventional studies.

The sputum samples will be processed and quantitatively analyzed to get a profile of the cytological composition.

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Please refer to this study by its ClinicalTrials.gov identifier: NCT01633385